Compressors are one of several components in cooling and heating systems. They are an important component as the compressor is used to compress refrigerant gas used in the system, raising the pressure and the temperature of the gas. The compressor is typically used in combination with a condenser, expansion valves, an evaporator and blowers to heat or cool a space. Depending on the direction of the refrigerant flow upon exiting the compressor, the system can be used to remove heat from a preselected space or provide heat to a preselected space.
The compressor itself typically is a hermetically sealed device that has an intake port and a discharge port. The hermetically sealed device typically is a metallic shell that houses an electric motor and a mechanical means, such as pistons or other mechanical portion, for compressing gas. For most compressor designs, the gas cavity enclosed by the housing serves as a reservoir of low-pressure gas to be drawn into the mechanical section of the compressor. The electric motor is connected to a power source that provides line power for operation. The motor in turn drives the means for compressing gas. Compressors are typically categorized by the means used to compress the gas. For example, compressors using a scroll compression device to compress refrigerant gas are referred to as scroll compressors; compressors using a piston device to compress the refrigerant gas are referred to as reciprocating compressors; compressors using rotating screw devices to compress a refrigerant gas are known as screw compressors. While there are differences among the compressors as to how refrigerant gas is compressed, the basic principles of operation as set forth above are common among the compressors, i.e., gas is drawn in through the gas intake when the motor is energized, the gas is compressed in the mechanical portion of the compressor and the highly compressed gas is discharged through an outlet port.
While different compressor designs may result in different noise generation mechanisms and overall different noise profiles, there are common sources of noise for the various types of compressors. One common source of noise originates in the exhaust gas at the discharge where the noise takes the form of a pressure pulsation. Pressure pulsation in the exhaust gas typically generates discrete narrowband tones at the harmonics of the operating speed. The pulsation propagates from the compressor discharge mechanism downstream in the refrigerant gas. The pressure pulsation can transmit noise through the compressor housing at the point of discharge tube penetration, or can propagate further downstream and induce noise upon contacting other components of the refrigeration system. As can be seen, this sound is particularly undesirable when the system is located within, adjacent to or near a living area or a work area.
Various mufflers have been attempted to eliminate, reduce or otherwise attenuate pressure pulsation and compressor noise. For piston-driven compressors, mufflers are typically positioned inside the compressor housing on the discharge side of the cylinder head, also referred to as a discharge head. While a muffler having an expansion chamber located adjacent to the discharge head can prevent pressure pulsation from propagating downstream, it has been found that placement of an expansion chamber muffler adjacent the discharge head reduces operating efficiency of the compressor, while also increasing the overall size of the compressor.
What is needed is a compressor muffler system that sufficiently attenuates pressure pulsations generated by compressor operations without adversely affecting compressor operating efficiency.